Drilling machine



Aug. 17, 1954 J. GONZALEZ 2,685,515

DRILLING MACHINE Original Filed March 4. 1947 3 Sheets-Sheet 1 INVENTOR mzm A 8 17, 1954 J. GONZALEZ 2,686,515

DRILLING MACHINE Original Filed March 4. 1947 3 Sheets-SheQc 2 i .{Z INVENTFDR E. BYWW ATTORNEYS Aug. 17, 1954 J i Z' v 2,686,515

DRILLING MACHINE Original Filed March 4. 1947 3 Sheets-Sheet 3 lllllillh'lllllll] I INVENTQR l E- BYW T :1

Patented Aug. 17, 1954 UNITED STATS TENT DFFICE Original application March 4, 1947, Serial No.

732,226, new Patent No. 2,496,939, dated February 7, 1950.

Divided and this application June 14, 1949, Serial No. 98,934

Claims.

This invention relates to drilling machines and relates especially to drilling machines adapted to drill holes in hard, brittle materials such as glass, stone, hardened plastic materials, vitreous tiles and the like. This application is a division of my application, Serial No. 732,226, filed March 4, 1947, for Drilling Machine which issued as Patent No. 2,496,939, dated February 7, 1950.

It is a purpose of this invention to provide a drilling machine of the character referred to which is capable of rapid and effective drilling of hard, rigid bodies. It is a further purpose of this invention to provide a drilling machine which is capable of successfully drilling holes in hard, rigid bodies such as sheets of glass, tiles and the like while reducing breakage to a minimum. It is a further purpose of this invention to provide a drilling machine of the character referred to which is relatively simple and inexpensive to manufacture but which, nevertheless, is capable of rapid and eifective drilling of hard, rigid bodies with a minimum of breakage. It is a further purpose of this invention to provide an improved hollow drill bit which has outwardly directed slots in the cutting edge and which, while capable of extended periods of use involving substantial wearing away of the cutting edge of the drill bit, is strong and is maintained with the cutting edges adjacent the notches firmly held in undistorted position. It is a further purpose of this invention a to provide a drill bit whereby a hole may be drilled in a hard, rigid body and whereby, during the same drilling operation, a concentric recess surrounding the hole may be formed in the hard, rigid body.

Heretofcre the drilling of holes in hard, rigid bodies such as sheets of glass, vitreous tiles and the like has occasioned considerable dimculty. Large, expensive, heavy machines have been designed for this purpose but even in such case there has been excessive breakage or cracking of the article being drilled. This has been particularly the case upon attempt to drill holes in close proximity to each other or in close proximity to the edge of the particle being drilled. Such difficulties have been overcome according to the present invention. Notwithstanding that the drilling machine of my invention is relatively light in weight and aifords a readily portable unit, it is rapid in its action as is evidenced by the fact that my drilling machine is capable of drilling a hole through a /4 inch glass plate in only about thirty seconds. My machine is capable of use with a minimum of breakage as evidenced by the fact that I have repeatedly drilled holes the diameter of which is of the order of inch to 1 inch in glass sheets varying in thickness between inch and inch with the spacing between adjacent holes reduced to as little as 1% inch without breakage of the glass between the holes. So far as I am aware such minimizing of breakage has not been accomplished in the case of previously known drilling machines regardless of their costliness and size.

The drilling machine of my invention comprises several novel and advantageous features which are preferably employed in combination but which may be employed separately so as to obtain at least in part the benefits resulting from their use according to this invention.

In a drilling machine embodying this invention a drill bit is secured in axial alignment with a spindle that is mounted for rotational and longitudinal movement while maintained in fixed axial alignment. Features of this invention relate to the means for maintaining the axial alignment of the rotatable spindle and to the combination with the rotatable spindle of means for resiliently urging the spindle in the direction toward the cutting edge of the drill bit during rotation of the spindle. Other features of this invention relate to the means for effecting the rotation of the spindle with a minimum of moving parts while permitting the longitudinal movement of the spindle during rotation thereof. Another feature of this invention relates to the combination with the rotatable and longitudinally movable spindle of manually operable means for retracting the spindle during rotation thereof in the direction away from the cutting edge of the drill bit. Another feature of this invention relates to means for indicating the progress of the drill bit through an article being drilled without retracting the drill bit from the article.

Other features of this invention relate to the means whereby the spindle and the drill bit including the cutting edge thereof are maintained accurately in alignment. In preferred embodi-' ments of my invention adapted for protracted periods of use, I provide a drill bit comprising a hollow tube having outwardly extending slots which are open ended at the cutting edge and which extend rearwardly from the cutting edge throughout a substantial portion of the length of the tube. In this way the cutting edge of the tube can be subjected to extensive wearing away while at the same time preserving the outwardly directed slots in the cutting edge. A drill bit in the form of a hollow tube with elongated outwardly directed slots was previously regarded as incapable of successful use due to the fact that the slots so weaken the tube wall that distortion of the tube wall results under the influence of the forces exerted during drilling with resulting breakage of the body being drilled. It is one of the features of this invention that a cylindrical tube provided with elongated outwardly directed slots is provided with a clamping arrangement that is longitudinally slidable relative to the tube for positional adjustment adjacent the cutting edge of the tube. The clamping arrangement comprises an inner member in slidable contact with the inner surface of the tube and an outer member in slidable contact with the exterior surface of the tube and when the outer member is in such posi-.

tion as to substantially overlie the inner member, the portions of the tube between the slots in the tube are firmly held in place adjacent the cutting edge of the tube and distortion of the tube wall and breakage of the article being drilled are eiTectively avoided. As the cutting edge is Worn away, the clamping arrangement can be correspondingly retracted for resetting at any desired proximity to the cutting edge 01 the tube that it is desired to have maintained. By thus firmly and accurately maintaining the metal of the tube adjacent the cutting edge thereof and by accurately maintaining the axial alignment of the spindle to which the hollow drill bit is attached, minimum breakage of rigid brittle material is possible in the practice of my invention. The inner and outer members of th clamping arrangement are preferably independently slidable longitudinally of the tube and the inner member may conveniently be provided with a member which extends through at least one of the slots in the tube whereby the manual adjustment of the inner member of the clamping arrangement is facilitated.

It is a further feature of this invention that may optionally be employed that cross member means is provided which extends through slots in the tube so as to project substantially beyond the periphery of the tube, which is in spaced relation to the cutting edge of the tube, and which is restrained from rearward movement. The cross member means affords effective means for producing a recess in the article or body being drilled that is concentric to the hole which is drilled. The cross member means may be associated with the clamping arrangement in any of the manners that are described more in detail hereinbelow or may be otherwise carried by the cylindrical tube intermediate the ends thereof.

Further purposes, features and advantages of this invention will be apparent from the following description of the typical embodiment of my invention which is shown by way of illustration in the accompanying drawings, wherein Fig. 1 is a plan view of a drilling machine embodying my invention;

Fig. 2 is a left-hand end elevation of the drilling machine shown in Fig. 1;

Fig. 3 is a sectional elevation of a portion of the drilling machine taken on the line 33 of Fig. 1;

Fig. 4 is a left-hand end elevation of the portion of the machine shown in Fig. 3;

Fig. 5 is a section of the adjustable frame support of the drilling machine taken on the line 5-5 of Fig. 1;

Fig. 6 is a plan sectional detail View taken on the line 6-5 of Fig. 2;

Fig. 7 is a front elevation of an alternative tubular drill of relatively large size together with an adapter for holding same secured to the spindle of the drilling machine;

Fig. 8 is an end view of the tubular drill and adapter shown in 7, viewing these parts from below;

Fig. 9 is a front elevation of an alternative form of tubular drill bit which embodies this invention and which includes an adapter to accommodate the drill bit to other drilling machines;

Fig. 10 is similar to Fig. 9 with some of the parts shown in section and showing the relation of the parts to a body in which a hole has been drilled that is surrounded by a concentric recess;

Fig. 11 is an end view of the drill bit shown in Figs. 9 and 10, viewing the parts from below, and

Fig. 12 is a detail view similar to Fig. 10 and showing the lower end of the drill bit as provided with an alternative cross member adapted for producing a recess having a tapered wall surrounding a drilled hole, and with an alternative form of centering plug.

Referring to the embodiment of this invention which is shown in Figs. 1 to 6, the drilling machine may be mounted on a suitable table or plate 28, to which the upright supports 2! may be secured as by suitable screws or bolts 22. Secured to and between the upright supports 2! are the L-shaped bars 23 which are disposed so as to provide a flat upper surface which is divided by a space between the innermost edges 24 of the bars 23. Supported by the L-shaped bars 25 is the carriage 25 which is mounted so that its position along the L-shaped bars 23 may be adjusted as desired. This may be accomplished in any suitable way, as by the bolts 2%; which are provided with enlarged head members 2'! that underlie the L-shaped bars 23 so that by tightening the nuts 28 the carriage 25 may be firmly clamped in place. By loosening the nuts 28, the position of the carriage can be adjusted along the longitudinal extent of the L-shaped bars The means employed to clamp the carriage 25 to the L-shaped bars 255 is shown in detail in Fig. 5.

Secured to the carriage 25 is a suitable motor 29, which may be an electric motor, having the power shaft 3! Also secured to the carriage 25 is the bracket 3!. The bracket iii is secured to the carriage 25 by the bolts 32 which, when loosened, are slidable in the elongated slots 33 in the carriage The elongated slots are provided so that the position of the bracket 3! may be adjusted relatively to the power shaft 30 for tightening the belt 3'3. To adjust the position of the bracket, a set screw 35 is used which is in threaded engagement with the ear member 3% that is rigidly secured to the carriage 25. The end of the set screw 35 abuts the end of the bracket 3i so that by turning the set screw the position of the bracket 35 relative to the carriage can be adjusted for tightening the belt 3d. After the belt has been adjusted to the desired tension, the bolts 32 may be tightened down so as to hold the bracket 3! rigidly in place.

At the outer end of the bracket 3! is a bearing which is indicated generally by the reference character 3? and which is adapted to maintain the spindle 3% in fixed axial alignment while permitting both rotational and longitudinal movement of the spindle 38. It is one of the features of this invention that the bearing 3! is specially constructed so as to maintain with very great accuracy the axial alignment of the spindle 38 during rotation of the spindle notwithstanding the occurrence of wear at the interface between the spindle and the bearing. To this end,

the bearing 31 comprises a bushing 39 which contains a longitudinally extending split 40 that permits contraction of the bushing 39 so as to compensate for wear at the interface between the bushing and the spindle 38. The bushing 39 is held in place by the arms 4| which contain trough-shaped portions surrounding the bushing 39 and the extremities of which are slightly spaced from each other. By tightening the bolts 42, the extremities of the arms 4| can be drawn together so as to constrict the bushing 39 and insure its being in closely fitted contact with the spindle 38. It is one of the features of this in vention that the force exerted by the bolts 62 is resiliently applied to the arms 4! by the use of lock washers 53 or the like. In this manner, if the tightness of the fit of the bushing about the spindle 33 is initially adjusted as desired by tightening the bolts 42, any progressive wear at the interface between the spindle and the bushing will be compensated by the action of the lock washers 53 in urging the extremities of the arm 6! together so as to maintain a close fit between the bushing 39 and the spindle 38 at all times. Even a slight amountpf wear at the interface between the spindle 38 and the bushing permits, at least to some extent, wobbling of the spindle 38 during use of the drill. In such case, there is danger of breakage of hard, brittle material such as glass during the drilling operation. By the arrangement above described, I have found that the axial alignment of the spindle 38 can be maintained extremely accurate during operation of the drilling machine over a long period of time, and that the accurate alignment thus obtained is an important factor in minimizing breakage. In the bearing above described, the bushing can initially be held in place prior to drawing the ends of the arms 4| together by any suitable means such as the set screw 44.

The spindle 38 is rotated in the bearing 3'i by the belt 3 2 which passes over the pulley 45 secured to the power shaft 33 and the pulley 45 secured to the upper end of the spindle 38. With this arrangement, the spindle 38 can be moved longitudinally through a substantial distance while the rotation of the spindle is maintained. The moving parts are reduced to a minimum which results in economical construction and also lcng life. Any wear at the pulleys can be compensated for by adjusting the tension of the belt 3 5.

As best shown in Figs. 2 and 3, means has been provided for resiliently urging the spindle in the direction toward the cutting edge of the drill bit carried by the spindle while the spindle is maintained in rotation. A preferred means for accomplishing the action referred to comprises the bar t's which at one end thereof carries a thrust bearing 48 that bears against the smallrounded boss 49 at the upper end of the spindle 33. With this arrangement, the inclination of the bar 31 relatively to the spindle 38 can be varied considerably while permitting the free rotation of the spindle 38 with the upper end thereof in contact with the thrust bearing 48. Adjacent the other end of the bar 41 is an aperture 50 which fits about a post which is upstanding from the bracket 3! parallel to and spaced from the spindle 38. The post 5| is surrounded by a compression spring 52 which bears against the end of the arm ll and urges this end of the arm upwardly. At an intermediate point between thrust bearing 48 and the post 5|, a manually adjustable fulcrum member is provided, which,

6. in the embodiment shown, is in the form of the wing nut 53 which is in threaded engagement with an elongated bolt 54 that is rigidly carried in the boss 55 upstanding from the bracket 31 by the lock nut 56. The bolt 54 passes through an aperture 51 in the bar 47. By adjusting the wing nut 53, the bar 4? can be tightened against the compression spring 52, and the force exerted by the compression spring 52 is transferred to the thrust bearing 48 so as to resiliently urge the spindle during the rotation thereof in the direction toward the cutting edge of the drill bit carried by the spindle 38. The resilient force applied to the spindle 33 urges the cutting edge of the drill bit against a body to be drilled so that the force applied is constant. This also is important in minimizing breakage of hard and brittle bodies. During the drilling operation, the spindle moves gradually downwardly as it rotates until the desired amount of drilling has been accomplished.

In order to quickly retract the drill after a drilling operation has been accomplished and while maintaining the rotation of the spindle 38, I provide means for urging the spindle 38 upwardly against the force applied by the resilient means for urging the spindle in the direction toward the cutting edge of the drill bit. As more particularly shown in Fig. i, I provide a lever 58 which is pivoted about a pin 59 which is rigidly secured to the bracket 3!. At one end of the lever 58, there is carried a roller 60. The end of the lever which carries the roller 69 is held in normally retracted position by a small tension spring 65 which is connected at one end to the lever 58 and at the other end to the bearing 37. By depressing the end 62 of the lever '58, the roller 6!! can be brought into contact with the lower surface of the pulley 56 and force can be applied through the lever for urging the pulley 55 and the spindle 38 on which it is carried upwardly to the amount desired for withdrawing the drill bit from the article in which a hole has been drilled. During normal operation of the machine while it is being used for drilling, the lever 58 is in the position shown in Fig. 4.

It is frequently desirable to determine the progress of a drill bit during a drilling operation without withdrawing the drill bit from the hole that is being drilled by the drilling machine. A simple means for accomplishing this result is shown in the accompanying drawings, particular reference being made to Figs. 2 and 6. A small rod 63 is slidably mounted in a boss E54 protruding from a bearing 31. The rod 33 is disposed parallel to the spindle 38 and the upper end of the rod underlies the marginal portion of the pulley 46. The upper end of the rod 63 can be placed in any desired position and fixed in this position by tightening the wing bolt 65. The use of rod 63 may be illustrated as follows. If the end of the drill bit is placed in contact with a work piece and if it is desired to drill into the work piece to the extent of inch, the upper end of the rod 33 may be positioned inch below the undersurface of the pulley 46. During the drilling operation, the spindle moves downwardly, and when the pulley 45 comes into contact with the upper end of the rod 63, the operator is immediately advised of the fact that the drill bit has penetrated A, inch into the work piece except for such wear as may have occurred at the cutting edge of the drill bit.

The construction of the improved drill bit which constitutes one of the features of this invention is shown particularly in Figs. 2 and 3. The drill bit is hollow and comprises a cylindrical metal tube 66. One end of the tube 88 is in frictional engagement with the support plug 61 which is centrally and internally threaded for securement with the threaded end 88 of the spindle. The drill bit and spindle are thereby maintained rigidly in alignment. To prevent relative rotation of the metal tube 56 with respect to the support plug 6?, the support plug may be provided with a small pin Ell that fits within a notch in the upper edge of cylindrical tube 56. The cylindrical tube 6'6 is of substantial length so as to allow for gradual and substantial wearing away of the cutting edge iii. The cylindrical tube 56 is provided with four outwardly directed slots H which are open ended at the cutting edge iii and which extend throughout a substantial portion of the length of the cylindrical tube 56. While four slots H are employed in the embodiment shown, any other number of slots may be employed depending largely on the diameter of the cylindrical tube. The tube 68 may be made of any suitable material such as brass, steel or the like.

The provision of the elongated slots ii in the cylindrical tube 86 allows for extensive gradual wearing away of the cutting edge of the tube while affording at all time the provision of one or more slots at the cutting edge, which ordinarily are desirable for obtaining proper cutting action of the tubular drill bit. The provision of the elongated slots presents difficuities, however, due to the fact that during a drilling operation the forces applied to the portions of the metal tube between the slots tends to result in distortion which, even though slight, is a major cause for breakage of hard, rigid bodies. I have found that this difficulty can be successfully overcome by providing longitudinally slidable clamping means, the position of which can be adjusted in the region of the slots in the tube 98 so as to be at any desired position adjacent the cutting edge of the cylindrical tube. In the embodiment shown, the slidable clamping means comprises an inner member E2 in the form of a ring which is in slidable engagement with the inner surface of the tube 65. An outer member 73 is also provided in the form of a ring which is in slidable engagement with the external surface of the tube 66. Preferably, the members 12 and 73 are independently slidable longitudinally of the tube. When the outer member 73 has been brought into position so that it substantially overlies the inner member 12, the portions of the tube between the slots ii are firmly clamped in position. By relative movement of the members 72 and '53 so as to be brought into non-overlying position, the position of these members relative to the longitudinal extent of the tube can be readily adjusted. In normal use of the drill, the members it and T3 are brought t clamping position at a distance spaced from the cutting edge of the drill which is somewhat in excess of the depth, of the hole to be drilled. For example, if the drill is to be used in drilling a sheet of glass inch in thickness, the clamping members 12 and '53 may be placed in the neighborhood of to inch from the cutting edge of the drill. In this manner, the portions of the tube between the slots at the cutting edge are held firmly in place and are prevented from any movement or distortion which might result in breakage of the work piece. After the cutting edge of the drill has been worn away as a result of many drilling operations, it it relatively simple to readjust the position of the clamping members i2 and 73 so as to maintain their desired distance from the cutting edge f the drill. This operation can be repeated until virtually all of the cylindrical tube has been worn away, When the ylindrical tube 66 has worn out it can readily be replaced with a new tube.

It is apparent from the foregoing that a very effective drill bit is afiorded which has a very long wearing life and which, at the same time, is free from objectionable distortion. The drill bit is economical to produce because it is a very simple operation to cut longitudinally extending slots in a metal tube. While the slots H in the embodiment shown are in alignment with the axis of the tube 66, this is not essential, for it is apparent that the slots ii, if desired, could be in some other form such as spiral form. However, for economy in production, it is normally the case that the slots H are in alignment with the axis of the cylindrical tube 66.

In the embodiment shown in Figs. 2 and 3, there is associated with the clamping members 12 and is the cross member means afiorded by the pins it which pass through slots H disposed on opposite sides of the cylindrical tube 68. The pins id may be secured either to member 12 or to member 13, although it is preferable to secure them to the member 72 as shown so as to afford means on the exterior of the tube 66 for adjusting the position of the inner member 12 of the clamping arrangement. Cross member means such as the pins it enables one to produce a concentric recess about a hole which is drilled by the cutting edge ill of the tube 63. Thus, when a hole has been drilled by the cutting edge ill, continued movement of the spindle 38 in a direction toward the cutting edge of the drill bit will bring the pins 1 3 into contact with the surface of the work piece. By continued rotation of the drill with the pins i l in pressure contact with the work piece, the surface of the work piece will be worn away so as to produce a recess which is concentric with a hole drilled by the cutting edge of the tube 66. The employment of the pins id, or equivalent cross member means, is not necessary in the practice or" this invention inasmuch as the clamping arran ment can be used in the absence of such cross member means. When the cross member means is not used, then the drill functions in the ordinary way for drilling a hole in a work piece. However, by employing the cross member means, it is in some instances desirable in employing the drilling machine of this invention to not only drill a hole in a work piece, but also produce a. recess which is concentric with the hole. This is one of the advantages of the drilling machine of the present invention.

If it is desired to produce a hole which is to be centered on a point indicated on a work piece, the centering plug l6 may be employed. The centering plug 75 fits slidably within the tube 66 and has clipped to the end thereof within the tube a backing spring it which normally holds the centering plug l5 adjacent the end of the tube 66, but which permits the centering plug to be retracted. By placing the point of the centering plug 15 on the center point of the hole to be drilled, the drill can be accurately set in position and the spindle lowered so as to start the initial drilling of the hole by the action of the cutting edge ill of the drill bit. For drilling holes in articles which are relatively thin, it is not necessary to withdraw the centering plug 75 from the tube G6. However, it is one of the advantages of this invention that the centering plug can be bodily removed from the cylindrical tube 66 after the drilling operation has been initiated. After the drilling operation has been initiated and after the centering plug and backing spring have been removed from the cylindrical tube E6, the drilling operation can be continued to afford a hole of any desired depth.

In the embodiment of this invention shown in Figs. 1 to 6, the drill bit which is illustrated is appropriate for drilling a hole of moderate size. For drilling larger holes up to several inches in diameter. a similar type of drill bit may be employed and a large size drill bit is shown by way of illustration in Figs. 7 and 8. In this embodiment of my invention, a cylindrical tube T! is employed which is of relatively large diameter and which, because of its relatively large diameter, contains a greater number of slots '58 than the number of slots used in the embodiment of my invention shown in the preceding figures. In order to prevent distortion of the portions of the tube ll between the slots '58, a clamping arrangement is employed which is similar to that shown in the preceding figures. Thus, in Figs. 7 and 8 there is an inner member E9 in the form of a ring which fits in slidable contact with the inner surface of the cylindrical tube ii. There is also the outer member Bil in the form of a ring which fits in slidable engagement with the outer surface of the cylindrical tube ll. When the member 89 overlies the member 15, the portions of the tube between these members are firmly clamped in position. The position in which these members may be clamped can, of course, be adjusted as desired.

The cylindrical tube l1 shown in Figs. '7 and 8 may be secured to the end of the spindle 38 by a support plug similar to the support plug 67 shown in the preceding figures. However, for accommodating cylindrical tubes of diiferent diameters, a spider support member 8| is shown in Figs. 7 and 8. This support member comprises three arms with notches in the underside appropriate for receiving the upper end of cylindrical tubes of different diameter. The cylindrical tube 11 is shown inserted into one of the sets of notches appropriate therefor. In the center of the support member 8| is an internally threaded hole 83 which is adapted for threaded engagement with the threaded end 68 of the spindle 38.

In Figs. 9, 10 and 11, an alternative form of drill bit is disclosed wherein an alternative clamping arrangement and alternative cross member means are employed. The drill bit shown in Figs. 9, 10 and 11 is adapted for drilling a hole which is somewhat larger in size than the hole which is drilled using the drill bit shown in Figs. 2 and 3. The drill bit comprises a hollow metal tube 84 which is held in frictional engagement with the support plug 85. The support plug 55 is provided with the pin 35 which engages the notch 87 in the upper edge of the cylindrical tube 84. The support plug 85 is provided with a central threaded bore 88 which is adapted for threaded engagement with the threaded end 66 of the spindle 38. However, in Figs. 9 and 10, an adapter member 89 is shown which has a threaded stem at for threaded engagement with the bore 88. The adapter member 89 can be secured firmly in place by application of a wrench to the hex enlargement 92, The upper end of the adapter 89 can be gripped by any conventional drilling machine such as a hand-operated electric drill. While it is preferable to employ the complete drilling machine of my invention as shown in Figs. 1 to 6 in order that the drill bit may be rotated in accurately maintained alignment so as to minimize breakage, one can use the improved drill bit of this invention using other types of drilling machine. For example, in the case of tile which has been set in place in a side wall, a hand-operated electric drill of conventional type may be used with the new drill bit of this invention for drilling a hole in the tile.

The cylindrical tube 84 is provided with four elongated outwardly directed slots 93. The portions of the cylindrical tube 84 between the elongated slots 93 are maintained firmly in position adjacent the cutting edge of the tube by the slidable clamping arrangement. In the embodi-. shown in Figs. 9, l0 and 11, the clamping arrangement comprises a cylindrical plug meme ber 9 which is in slidable engagement with the inner surface of the cylindrical tube 84. In the lower surface of the cylindrical plug member 96, there is a groove in which the cross bar 95 fits in frictional engagement therewith. The lower edge or the cross bar 95, as shown, is flush with the lower surface of the plug member 95%. In slidable contact with the exterior surface of the tube 34 is the collar member 9%. When the collar 95 is in non-overlying relation with the plug member es, the position of the members 9 1 and 96 can be adjusted relatively to the tube 84 so as to be at predetermined desired distance from the cutting edge S la of the tube. By moving the collar so as to overlie the plug member 94, the portions of the tube 8:3 between the slots 93 are clamped firmly in position as described more in detail hereinabove.

In Fig. 10, the drill bit is shown in its relation to a work piece 9'5 which may, for example, be a sheet of glass; The cutting edge of the drill bit has penetrated through the work piece to produce the hole 98. The drill bit, including the cross bar 95, is shown in the position which it occupies as a result of continuing to rotate the drill bit while the cross bar 95 is in pressure contact with the work piece 9?. Such continued rotation causes the cross bar 95 to produce the recess 99 in the upper surface of the work piece, this recess being concentric with the hole 98. The diameter of the recess 99 may be varied by varying the position of the cross bar 95 relatively to the tube 84. In Figs. 9 and 10, the cross bar 95 protrudes slightly further to the left-hand side than to the right-hand side of the tube 9 3 so that the recess 99 is somewhat larger in diameter than if the cross bar protruded an equal distance from each side of the tube 84. By fitting the cross bar 95 in frictional engagement with the groove in the plug member at, the position of the bar 95 can be adjusted as by tapping it lightly with a hammer. Of course, the cross bar 95 may, if desired, be rigidly secured to the plug member 94.

In Fig. 12, the parts of the drill bit shown are the same as those shown in Figs. 9 to 11, and are indicated by like reference characters, except that in the Fig. 12 the cross bar that is employed is the cross bar I00 which presents rearwardly inclined surfaces lill on each side of the tube as. A cross bar such as the cross bar we shown in Fig. 12 may be employed when it is desired to produce in the work piece Hi2 a recess having an inclined side wall surrounding the hole cut in the work piece by the cutting edge of the drill bit.

In Fig. 12, a modified type of centering plug is shown which may be used with a clamping arrangement of the type shown in Figs. 9 to 12. As shown in Fig. 12, the centering plug I03 fits in the end of the tube 84 and is provided with a conical backing spring 194. The centering plug may be used in the manner that has been described hereinabove in connection with the embodiment of this invention shown in Figs. 2 and 3. After the centering plug has been used to properly lcate the hole to be drilled, the centering plug, together with the backing spring, can be removed bodily as soon as the outline of the hole has been formed in the work piece by the cutting edge of the drill bit.

In the embodiments of this invention shown in Figs. 9 to 12, the cross bar 85 shown in Figs. 9 to 11 and the cross bar we shown in Fig. 12 may, of course, be dispensed with if it is desired to do so.

The operation of the drilling machine of this invention is believed to be apparent from the foregoing description. A work piece 65 may be placed on a suitable support on the table 20. The lateral position of the carriage is first adjusted so as to be in proper relation to the work piece and the carriage is then secured in place by tightening the nuts 28 on the bolts 2%. The motor is then started and by adjustment of the wing nut on the bar i? the spindle and the drill bit in axial alignment therewith are brought down so as to just contact the surface of the work piece. If desired, the centering plug may be em ployed to assist in properly positioning the drill bit. The wing nut 53 is then further adjusted so that the cross bar will be in approximately a horizontal position, for when the cross bar is in this position an appropriate amount of resilient force is applied to the spindle as it rotates to urge it in the direction of the cutting edge of the drill bit. A suitable abrasive material is placed about the end of the drill bit so that it will be carried by the outwardly directed slots in the cutting edge. Any abrasive material may be used such as Carborundum powder in turpentine as a carrier. For some materials it is not necessary to employ an abrasive, although it is usually desirable to at least employ water so as to cool the end of the drill. In the case of a material such as glass, it is usually necessary to use an abrasive powder, All that is necessary to drill the hole is to start the motor and the machine automatically drills the hole to the desired depth into or through the work piece. After the hole has been drilled, the operation of the motor is continued, and by depressing the end 312 of the lever 58, the drill bit is retracted from the hole. If the centering plug has been used to initially locate the drill bit in reference to the work piece, the spindle and drill bit can be retracted by use of the lever 58 after the outline of the hole to be drilled has been formed in the surface of the work piece, thereby permitting removal of the centering plug. The spindle and drill bit thereafter may be lowered to afiord pressure contact with the Work piece and the drilling operation may be completed.

If it is desired to produce a recess in the work piece surrounding the hole that is drilled, the drill is provided with a cross bar or other suitable cross member means of the type described above and the rotation of the drill bit is contin ued while the cross member means is in contact with the work piece and until a recess of the desired depth is produced. A suitable abrasive can be used to assist the action of the cross member means in producing the recess. The surface of the cross member means is, of course, worn 12 away to some extent in forming a recess, but when the cross member means is worn it is a relatively simple matter to replace it with the new one.

While the drilling machine shown in Figs. 1 to 6 comprises a drill bit in the form of a cylindrical tube having elongated slots combined with adjusting clamping means, it is not essential that the drilling machine be used with the par ticular type of drill bit which has been described in detail hereinabove. Thus, a hollow cylindrical tube with shallow outwardly directed notches in the cutting edge may be used, and in such case it is not necessary to employ the adjustable clamping arrangement. However, by employing the elongated slots in the cylindrical metal tube in combination with the adjustable clamping arrangement, a very inexpensive drill bit is afforded which is capable of prolonged periods of usage and which at the same time is free from objection because of distortion of the metal of the tube.

While this invention has been described in connection with certain specific embodiments shown in the accompanying drawings, it is to be understood that this has been done merely for the purpose of illustrating a typical preferred embodiment of my invention and that the scope of my invention is to be governed solely by the language of the following claims.

I claim:

1. A drilling machine comprising a spindle, a bearing for said spindle adapted to permit rotational and longitudinal movement of spindle while maintaining fixed the axial alignment of said spindle, a drill bit that is attached to said spindle in axial alignment therewith and that has a cutting edge at the end hereof, means rotating said spindle in said bearing and means for resiliently urging said spindle for movement in the direction of the cutting edge of said drill bit while maintaining the rotation of said spindle, said means for resiliently urging said spindle for movement in the direction of the cutting edge of said drill bit while maintaining the rotation of said spindle comprising a bar member having a thrust bearing bearing against the end of said spindle opposite to said drill bit, resilient spring means bearing against said bar member at a position spaced from said thrust bearing and in a direction counter to the direction of movement of said spindle toward said cutting edge of said drill bit, and fulcrum means bearing against said bar at a position between said thrust bearing and said resilient spring means and arranged to transfer the force exerted on said bar member by said resilient spring means to said thrust bearing but in the opposite direction, and means to adjust the position of said fulcrum means in the direction of longitudinal movement of said spindle.

2. A drilling machine comprising a support, a bracket secured to said support and projecting substantially from said support, a spindle, a bearing that is secured to said bracket adjacent the end thereof remote from said support and that is adapted to permit rotational and longitudinal movement of said spindle therein, a drill bit that is attached to said spindle in axial alignment therewith and that has a cutting edge at the end thereof, means for rotating said spindle in said bearing and means for resiliently urging said spindle in the direction toward the cutting edge of said drill bit while maintaining the rotation of said spindle, said means for resiliently urging said spindle in the direction toward the cutting edge of said drill bit comprising a bar having a thrust bearing bearing against the end of said spindle remote from said drill bit, a first post that is carried by said bracket parallel to said spindle and spaced therefrom and that passes through an aperture in said bar spaced from said thrust bearing, a compression spring surrounding said first post between said bracket and said bar, a second post fixed to said bracket and parallel to said first post and passing through an aperture in said bar intermediate between said first post and said thrust bearing, and a fulcrum presenting member carried by said second post and adapted to bear against said bar and oppose force exerted on said bar by said compression spring, and means for adjusting the position of said fulcrum presenting member relative to said second post.

3. A drilling machine comprising a spindle, a bearing for said spindle adapted to permit rotational and longitudinal movement of said spindle while maintaining fixed the axial alignment of said spindle, a drill bit which is secured to said spindle in axial alignment with said spindle and which is provided with a cutting edge at the end thereof, means for rotating said spindle in said bearing, means for resiliently urging said spindle for movement in the direction toward the cutting edge of said drill bit while maintaining rotation of said spindle, and manually operable means for retracting said spindle in the direction away from the cutting edge of said drill bit, said means for retracting said spindle comprising a member that is fixed to said spindle for rotation therewith and that presents an annular lower surface and a manually movable lever that is pivotally mounted in fixed relation to said bearing and that is provided with a portion adapted to contact said annular lower surface of said member responsive to manual movement of said lever to urge said spindle in the direction away from said cutting edge of said drill during rotation of said spindle.

4. A drilling machine according to claim 9 wherein said member that is fixed to said spindle and that presents an annular lower surface is a pulley comprised in said means for rotating said spindle and wherein said portion of said lever adapted to contact said annular lower surface is a roller rotatably carried by said lever for rolling contact with said surface during rotation of said pulley.

5. A drilling machine comprising an elongated horizontally disposed support, a carriage mounted on said support for movement relative to said support for positional adjustment relative to the longitudinal extent of said support, means for securing said carriage to said support when in any of a plurality of positional adjustments relative to the longitudinal extent thereof, a bracket protruding from said carriage in secured relation thereto and disposed transversely to the longitudinal extent of the support so as to clear said support, a vertically disposed spindle mounted for rotation and vertical movement in a bearing adjacent the end of said bracket, a power shaft rotatably mounted on said carriage, means for rotating said power shaft, a belt drive between a first pulley secured to said power shaft and a second pulley secured to said spindle for effecting rotation of said spindle responsive to rotation of said power shaft, and means for resiliently urging downward movement of said spindle during rotation thereof for I4" exerting a predetermined pressure between the cutting edge of a drill bit secured to the lower end of said spindle and a work piece disposed in contact therewith.

6. A drilling machine comprising a spindle, a bearing adapted to permit rotational and longitudinal movement of said spindle, a drill bit secured to said spindle in axial alignment with said spindle and having a cutting edge at the end thereof, and means for urging said spindle in the direction of the cutting edge of said drill bit while maintaining the rotation of said spindle, said bearing comprising a constrictable bushing having substantial extent longitudinally of said spindle in closely fitting contact with said spindle, a constrictable bushing holder for holding said bushing therein, said bushing and said bushing holder being adapted to exert resilient resistance to constriction thereof, and resilient means for constricting said constrictable bushing holder and adapted to continuously exert resilient force effective to constrict said constrictable bushing holder and said constrictable bushing held therein for automatically constricting said bushing responsive to said resilient force continuously exerted by said resilient means so as to compensate for wear occurring at the interface between said bushing and said spindle thereby continuously and automatically maintaining pressure contact of said bushing with said spindle notwithstanding wear at the interface between said bushing and said spindle.

7. In a drilling machine comprising a rotatable spindle having secured to an end thereof a drill bit in axial alignment therewith, a bearing for accurately controlling the axis of rotation of said spindle therein, said bearing comprising a tubular bushing of substantial extent longitudinally of said spindle and having a longitudinally disposed slot therein extending throughout the length thereof that permits constriction of said bushing to constrict the inner surface of said bushing against the peripheral surface of said spindle, and a bushing holder for said longitudinally split bushing, said bushing holder comprising a pair of arms that emanate from a common support, that have substantially spacedapart ends disposed substantially oppositely with respect to said support and that have troughed portions between said support and said ends adapted to press against said bushing to constrict same upon urging said ends of said arms toward each other, and arm-end holding means coacting with said ends of said arms which comprises resilient means adapted to continuously exert resiliently applied force effective to urge said ends of said arms toward each other for constricting said bushing against the peripheral surface of said spindle and thereby automatically and continuously maintain contact pressure between said bushing and said spindle notwithstanding substantial wearing away of the interface between said bushing and said spindle.

8. In a drilling machine according to claim '7, the bearing recited in said claim wherein said arm end holding means comprises a bolt and resilient means in the form of a member surrounding said bolt which is resiliently compressible longitudinally of said bolt, said bolt and said member being adapted to coact with said ends of said arms to hold said member compressed between a part of said bolt and the end of one of said arms, and said member when so held in compressed condition being adapted to continuously exert resiliently applied force against said arm end effective to urge said arm ends toward each other and to constrict said bushing against said spindle for automatically maintaining said contact pressure therewith notwithstanding substantial wearing away of the interface between said bushing and said spindle.

9. A drilling machine comprising a spindle having secured to an end thereof a drill bit in axial alignment therewith and a bearing adapted to permit rotational movement of said spindle While maintaining fixed the axial alignment of said spindle, said bearing comprising a bushing of substantial longitudinal extent that surrounds said spindle except for a longitudinally disposed slot extending throughout the length of said bushing which permits constriction of said bushing to constrict the inner surface thereof against said spindle in closely fitting contact with said spindle, a constrictable bushing holder for said bushing, and resilient means for constricting said constrictable bushing holder which is adapted to continuously exert resiliently applied force eifective to constrict said bushing holder and said bushing therewithin for maintaining the inner surface of said bushing constricted against the stantial longitudinal extent conforming to the periphery of said spindle and which surrounds said spindle except for a longitudinally disposed slot extending throughout the length of said member, said member being bendable to bring opposed margins of said slot into closer proximity and thereby constrict said inner bearing surface presented by said member against the periphery of said spindle, mounting means for said member, and means adapted to continuously exert resiliently applied force on said member effective to bend said member as aforesaid and to automatically and continuously maintain said inner bearing surface presented by said member in pressure contact with said spindle notwithstanding wear at the interface between said inner bearing surface of said member and said spindle.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 137,435 Gillespie Apr. 1, 1873 306,477 Fuller Oct. 14, 1884 922,649 Williams et a1. May 25, 1909 1,048,059 Foppiano Dec. 24, 1912 1,385,732 Taylor July 26, 1921 1,406,185 Hansen Feb. 14, 1922 1,453,239 Dostal Apr. 24, 1923 1,674,317 Buff June 19, 1928 1,849,963 Snow Mar. 15, 1932 1,988,538 Brown Jan. 22, 1935 2,151,205 Hawn Mar. 21, 1939 2,334,453 SWOffOId NOV. 16, 1943 2,413,084 Sommer et al Dec. 24, 1946 

